Core recovery apparatus



Nov. 6, 1956 G. BURGESS 2,769,615

' CORE RECOVERY APPARATUS Filed April 6, 1953 P m A I g 2 27 29 h l I fI 1.33 1' k; l 2 14 I E [8'1] I w l3 l9 [I g L i 2| 26 FIG. 4 BINVENTOR. 24 BY GERALD BURGESS I I ATTORNEY United States Patent OfificeCORE RECOVERY APPARATUS Gerald Burgess, Casper, Wyo. Application April6, 1953, Serial No. 346,840

4 Claims. (Cl. 25572) This invention relates to core recovery apparatusand more particularly to a core barrel by which successive cores may berecovered without removing the drill string from the well.

In drilling wells to attempt to locate a deposit of oil or gas,so-called cable tool drilling, in which a bit is reciprocated upwardlyand downwardly at the bottom of a hole by a cable, has many limitations,and has been largely replaced by rotary bit drilling. Furthermore, sincea sudden entry of the hole into an oil or gas deposit under considerablepressure has, in the past, often resulted in a blow-out, with aconsequent loss of tools and other equipment and sometimes a hazardousfire, it is now customary to pump mud down the bore such mud beinggenerally a slurry or suspension of certain clays and other materials toprovide adequate weight. Thus, the hydrostatic head of the column ofweighted mud in the bore is depended upon to produce sufiicient pressureto prevent gas at high pressure from blowing out the well. In addition,pump pressure may also be added to the natural hydrostatic head toincrease the pressure of the mud atthe bottom of the bore. However, dueto the mud pressure forcing mud into the well bore, it is sometimespossible for the bore to be drilled completely through a productivestratum, without the driller knowing it. Of course, the mud and thecuttings may be analyzed at every few feet of drilling, to minimize thepossibility of passing through a valuable stratum, but the bestinformation relative to the stratum being drilled through is obtainedfrom a solid sample of the stratum itself. Thus, it is customary,Whenever other evidence indicates the desirability thereof, orparticularly in wildcat wells, whenever there is a possibility of thebore approaching or passing through either a productive stratum or ageological marker, to take a core. A .core is usually obtained bydrilling with an annular diamond bit, and pulling up the column ofstratum left in the middle. It is possible, of course, to attach a corebit to the lower end of the drill string, lower the drill string intothe hole, drill downwardly for the desired distance, and then pull thedrill string to pull the core up with it, the lower'end of the drillstring being provided with a device for pulling the core up with it.However, the time consumed in putting down and pulling up the drillstring for each core renders such coring operations expensive, andincreasingly expensive as the depth of the bore increases. Thus, it isdesirable to use a removable core barrel or receptacle for the core,such a core barrel generally being removed from the well by a wire line.Previous removable core barrels have produced difficulties in operationand inadequacy in results, such as poor recovery due to blocking, unduewear of parts, and have involved unduly complicated parts. In addition,often a complete core has been thought to have been taken, but when thecore barrel is retrieved, very little core specimen is obtained.

Among the objects of this invention are to provide a novel core drillingapparatus, including a novel core barrel; to provide such apparatuswhich enables successive cores to be taken with relative ease; toprovide such apparatus which tends to insure that complete cores will berecovered; to provide such apparatus, during the use of which anindication may be given to the driller when ditficulty is beingencountered below; to provide such apparatus which is simple inconstruction; to provide a novel core barrel which may be moved up thedrill string by either a wire line or by reverse mud circulation; and toprovide such a core barrel which is effective and efllcient inoperation.

Additional objects and the novel features of this invention will becomeapparent from the description which follows, taken in connection withthe accompanying drawing, in which:

Fig. l is a condensed, vertical section of the lower end of a drillstring embodying core recovery apparatus constructed in accordance withthis invention;

Fig. 2 is a fragmentary vertical section taken adjacent the upper end ofthe core barrel and illustrating a difierent position of the same;

Fig. 3 is a transverse sectiontaken along line 33 of Fig. 1, adjacentthe lower end thereof;

Fig. 4 is an enlarged fragmentary vertical section taken at the lowerend of a top sub forming apart of the apparatus of Fig. l; and

Fig. 5 is an enlarged, partial vertical section taken at the lower endof the apparatus.

As illustrated in the drawing, core recovery apparatus constructed inaccordance with this invention may be attached to the lower end of thelowermost section 10 of drill pipe, and may include an upper sub Sconnected to the lower end of the drill pipe section 10, as by threads11, an outer tube 12 connected to the lower end of the upper sub S, asby threads 13, and a drill bit B, in turn attached to the lower end ofthe outer tube 12, as by threads 14. A removable core barrel, which ishollow and open at the lower end, is disposed within the assembly thusdescribed, and may comprise a head H, normally disposed adjacent theupper sub S, an inner tube 15 connected to the lower end of the head H,as by threads 16, and a lower guide G, connected to the lower end ofinner tube 15, as by threads 17. In addition, the core barrel may beprovided with an annular core recovery spring 18, disposed Within thelower guide G and provided with a series of lugs 19, which engage thelower end of inner tube 15 and prevent the spring 18 from movingupwardly within the core barrel along with the core. Of course, thespring 18 permits the core to move up into the barrel as drillingproceeds downwardly.

In accordance with this invention, the sub S is provided adjacent itslower end with a series or" radially spaced, inwardly extending wings20, which form slots 21 therebetween, as in Fig. 4, and which maintainthe core barrel particles of diamonds or the like, the matrix 24extendingacross the bottom and up both the inside and the outside of thelower end of the bit B. A series of radially spaced slots 25, as in Fig.3, may extend down the outside ofthe matrix 24, and also across thebottom and up the inside. As will be evident from Fig. 3, each of theholes 23 preferably terminates at one of the slots 25 in the diamondmatrix 24. The bit B may further be provided with a seat 26 for thelower end of guide G.

During the normal drilling of a core, the parts willv be disposed insubstantially the position shown in Fig. 1,

Patented Nov. 6, 1956' in which the main "body of the head H of the corebarrel isdisposedwithinthe series of-inwardly-extending wings 20 and theguide G'is disposed within Wings 22. 'The normal circulation of mud:will bedown throughthe sub'S, pastthe head of 'H of the core barrel,through slots 2j1' between the Wings' ZO, thence downwardly throughaniannular'space 27,fbetween;the outer tube 1 2 andtheinner'ttibe 15,through the slots "between lower Wing's 22,j which surround -the guide Gat the lower end of the core barrel, and finally through discharge holes2310 the bottom of the bit 'B.

' In furtheraccord'ance with this invention, a generally annular,enlarged or choke section 30 is formed infsub S immediately abovethewingsZtl with a section--29 of restrictedcross-sectional areaimmediately above.' The cross-sectional area ofhead H corresponds to thecrosssectional 'area of restricted'sec'tion 291, preferably justslightly less, and the choke section 30 is normally disfill to a markeddegree the requirements and objects,

hereinbefore set forth; As will be evident, the section of largercross-sectionalarea, such as the choke section V 30 and the section of'lesser cross-sectional area immediately thereabove, cooperate with .amovable. core barrel which is normally positioned so. as not tointerfere with the flow of mud through'the'section of reduced posedadjacent a tapering neckI31 of head H of the core barrel. Also, head Hmay "be provided with an upwardly extending'passage 32, which leadsfrom. a point on the outside of. the body of the head H normallyjustb'elow. wings '20, to the upper end of a central passage 33, whichextends downwardly within head H to the interior space within inner tube15. An initial flow of 'mud through passages 32 and 33 may provideinternal flushing for the core barrel, thus tending to prevent the corefrom becoming jammed with n the inner tube against cuttings or otherharder material. As the core moves upwardly in the barrel, the downwarddirection of passage 32 on the outside,.assists in permitting the .mudtrapped within the barrel to be easily forced out of the barrel by thecore, thereby permitting afull core tobe taken. Also, a wire linerecovery head 34 may be formed integrally with the head H or remov Vably attached thereto. 7

'As will be evident, as coring proceeds, the parts of the apparatus tendto stay in the'position of. Fig. l, the

core entering'the inner tube '15 of the barrel, as the bit B rotates andcuts an annular hole deeper. When the maximum length of core has beentaken, or in the event that the core becomes jammed or misaligned withinthe barrel, the core barrel will be prevented from moving downwardly asthe bit B moves downwardly, so that the 'head H of the barrel will moveto the position of Fig. 2,

In position, instead of the tapered neck 31 being opposite ,the chokesection 30, the larger,'main body of the head'H willbe within thechokesection 30, and

"the flow past the core barrel will be considerably restricted. As willbe evident, the head H is still within theguide wings when the flow isso restricted. This will be reflected, at the top of the well, inanincrease in the pressure necessary to maintain mud circulation,thereby indicating to the drillerthat the core barrel has moved upwardlywithin the sub S. If the difiiculty cannot be overcome by shiftingthedrill stem, or other stratagems, or if depth measurement indicates thatthe full length of core has been taken, the core barrel may beretrieved, as by reversing mud circulation to push the core barrel. upto the top of the drill string, in which event a. suitable catcher forthe core barrel, as

.ofconventional construction, is provided at the top of the drillstring.Or, a wire line and recovery tool may be run: down thevdrill string,for'engagement with the wire line recovery head34 provided at the top ofhead H of the 'core barrel. After the recovery of one core, the core.barrel ma'y be dropped back into the drill string and moved down withthe mud, ;or may be lowered by a wire line, so that another core may betaken without undue time delay. A s willbe evident, a number of coresmaybe taken in succession, with the timerequired for-movement of thecore barrel to and from the surface being held to a minimum. This 'i'saparticular advantage in exploratory drilling, wherein long sections of'thewell are often cored continuously. 'If desired, suitablecross-sectional area, and thereby 'indicate'to the driller when the corebarrel has moved upwardly in'the drill stem, in addition to indicatethat the core may be jammed or that some other undesirable event hasoccurred. The

lack of such an indication further furnishes information to the driller,i. e. that coring is proceeding in thep desired manner. In addition tothe quickness'and ease with which the core barrel may be movedbetweenbottom hole and the collar,-the simplicity of construction'of the coringapparatus of 'thisinvention not only "reduces the V initialj'c'ost,but'also the upkeep due to wear. [The 'parts involved are held togetherby conventional'threaded 'connections, which permit ready assembly anddisassembly, and there are no complicated mechanical con V V nectionswhich were'forrnerly thought necessary to attach siderably.

1 corebarrel is free to rotate in the drill stem, thereby a-corebarrelto a drill'stem. The mud flowing down past;the barrel also'tendsto.maintain it in position,

section 30, when the pressure of mud will'increase conthe. passagesleading to theinterior of the barrel tend'to clean the core asit entersthe'barrel, while the passages also permit'the mud trappedin the barrelto be forced outYby the rising core. As will also be evident, the

damage to the core, and'tending to assure that cores .of maximumdiameterwill be taken.

Although-specific embodiment of'this inventionhas been.illustra-ted anddescribed with particularity, it will be understood that otherembodiments may exist and that 7 various. changes may be made therein,all without departingfrom the: spin'tfand scope of this invention.Whatis claimed is: I i 1. In core drilling apparatus, including an'outertube,

, a hollow bit at the lower end of said tube, and -a hollow core barrelopen at its lower end and disposed :within said tube, the improvementwherein said tube includes agenerally cylindrical sub threadedlyattachableto the,

lower end of a section of drill-pipe, a cylindrical tube;threadedlyattachable :to'the lower endof said sub, and

a generally cylindrical drill bit threadedly attachable to. the lowerend of said cylindrical tube; said sub having anupper section ofrestricted cross-sectional area, an intermediate section of greatercross-sectional area and a lower section having a plurality of integral,inwardly extending wings, the. diameter at the inneredges of'said' Isaid drill bit-having-a plurality of inwardly extending" wings whoseinner diameter corresponds to thediameter wings corresponding to thediameter at said section of. restrictedfarea; said cylindrical tubehaving an inner diameter 'greater than said section of restricted area;

at said section of restricted area, an annular seat below said. bitwings for the lower end of said core barrel, a'

plurality-ofpassages leading from spaces between said bit wings to thelower end of said bit, and relatively harddrilling material attached tothe inside below said seat, to the bottom and to the outside of saidbit; and said core barrel having a cross-sectional area corresponding tosaid restricted area and being normally disposed below *said restrictedarea but movable upwardly tosaid restricted area to reduce thecross-sectional area availablefor flow of fluid downwardly past saidcore barrel.

-As. indicated, the flushing action provided by 2. In core drillingapparatus, including an outer tube, a hollow bit at the lower end ofsaid tube, and a hollow core barrel open at its lower end and disposedwithin said tube and movable upwardly and downwardly within said tube,the improvement wherein said outer tube is provided with a wall defininga fluid passage having a section of restricted cross-sectional areaabove a section of greater cross-sectional area, said wall beingprovided with a plurality of inwardly extending wings below said sectionof greater cross-sectional area, said wings having a greaterlongitudinal extent than said section of greater cross sectional area,said bit also having inwardly extending wings and the diameter at theinner edges of said Wings corresponding to the diameter at saidrestricted area, and said core barrel having an outer diametercorresponding to said restricted area and being normally disposed belowsaid restricted area but movable upwardly by the core to said restrictedarea to reduce the cross-sectional area available for flow of fluiddownwardly past said core barrel.

3. In core drilling apparatus, including an outer tube, a hollow bit atthe lower end of said tube, and a hollow core barrel open at its lowerend and disposed within said tube and movable upwardly and downwardlywithin said tube, the improvement wherein said tube is provided with awall defining a fluid passage having a section of restrictedcross-sectional area above a section of greater cross-sectional area,said wall having a plurality of inwardly extending wings below saidsection of greater cross-sectional area, the diameter at the inner edgesof said wings corresponding to the diameter at said section ofrestricted area; and said core barrel having at least adjacent its upperend a diameter corresponding to said restricted area and being normallydisposed below said restricted area but movable upwardly by the core tosaid restricted area to reduce the cross-sectional area available forflow of fluid downwardly past said core barrel, said upper portion ofsaid core barrel having suflicient longitudinal extent that a portionthereof is still Within said wings when the cross-sectional areaavailable for flow is reduced.

4. In core drilling apparatus, a hollow bit at the lower end ofincluding an outer tube, said tube, and a hollow core barrel open at itslower end and disposed within said tube, the improvement wherein saidouter tube is provided with a wall defining a fluid passage having asection of restricted cross-sectional area above a section of greatercross-sectional area; said core barrel includes a generally irnperforatehead, an inner tube threadedly attached to the lower end of said head, agenerally cylindrical guide threadedly attached to the lower end of saidinner tube and an annular core spring having outwardly extending lugsand disposed within said guide; said head having a generally solidcylindrical section, a frustoconical neck thereabove tapering upwardlyand a wire line recovery pin at the upper end, said neck being nor-".ally disposed opposite said outer tube section of greatercrosssectional area and said wire line pin being normally disposedopposite said section of restricted crosssectional area; saidcylindrical section of said head having a diameter corresponding to saidouter tube section or" restricted cross-sectional area so that uponupward movement of said core barrel said cylindrical section will moveupwardly to said section of restricted area to reduce the area availablefor flow of fluid downwardly past said core barrel; said cylindricalsection of said head also having a central passage extending to theinterior of said core barrel and an upwardly inclined passage leadingfIOIll the outside thereto adjacent the lower end to the upper end ofsaid central passage; and said guide being constructed and arranged toform a space beneath the lower end of said inner tube to receive saidoutwardly extending lugs of said core spring, said lugs engaging thelower end of said inner tube to restrict upward movement of said corespring.

I References Cited in the file of this patent UNITED STATES PATENTS2,164,598 Thrift July 4, 1939 2,189,057 Copelin Feb. 6, 1940 2,234,264Lang Mar. 11, 1941 2,347,726 Auld et a1. May 2, 1944 2,357,907 PhillipsSept. 12, 1944 2,565,101 Taylor Aug. 21, 1951 2,621,897 Brown Dec. 16,1952

